This is an R03 (PAR-09-223) application submitted to NIDDK. This study entails the revision of the 12-session Group Cognitive Behavioral Therapy (CBT-DM) manual for depressed Type 1 Diabetes Mellitus (T1DM) Latino youth, and explores both the absolute efficacy of CBT-DM against a treatment as usual (TAU) condition, and the added impact of CBT-DM over the original culturally-adapted CBT for depression. After initial manual revision by our expert team, in-depth interviews with diabetes treatment providers, and a small pre-pilot study with 8 depressed T1DM Latino youth and their parents will be conducted to inform the revision of and further refine CBT-DM treatment manual. Focus groups with youth and parents in the small pre-pilot study will serve to complete the refinement process. Finally, 60 depressed T1DM youth will be randomized to one of three conditions: CBT-DM, CBT for depression, and TAU. Treatment efficacy will be assessed by comparing changes on depression, self-esteem and functionality scores, diabetes self-efficacy and quality of life, and treatment adherence and self-care management of T1DM. We propose that both CBT-DM and CBT will be superior to TAU in reducing depression, and improving self-esteem and functionality. We also hypothesize that CBT-DM will be superior to the other conditions in domains related to T1DM (diabetes self-efficacy, quality of life, treatment adherence and self-care behaviors). Intake data will be obtained with structured diagnostic interviews, self-report scales and laboratory tests of glycosylated hemoglobin (HbA1c). We will assess youth T1DM health and treatment adherence information, mental health (including depression) diagnostic status, youth cognitive and affective variables, parent and family functioning, and family knowledge about youth depression and T1DM. We will also evaluate the feasibility and acceptability of treatment, the adequacy of randomization, attrition rates, therapist competence and treatment integrity. The assessment will be conducted at baseline, at weeks 5, 9 and 12 (post-treatment), and at the three- and six-month follow-ups. This investigation is the second step in a research program aimed to bring the benefits of evidence-based treatment (EBT) development to Latino youth with comorbid T1DM and depression, and set the stage for a larger-scale and definite study of treatment efficacy (R01). This study is innovative because it is the first that could potentially contribute to provide initial evidence in support of the probably-efficacious status of a psychosocial intervention aimed at both improving diabetes health status and reducing depressive symptoms in youth. The revised CBT-DM manual for T1DM Latino youth would also be an innovative clinical tool that could enhance the prevention of mood disorders and the reduction of health disparities in this minority group.